Hang in there! You'll get better with experience. My sister didn't start riding her hybrid until she was 60. She was very difficult to ride with--she laid on the brakes and swerved a lot. We once had to turn around on a trail, because she was sure she was heading into the ditch (don't stare at the ditch--just look straight ahead. Your bike will go where you are looking). Any trail that crossed a road, also involved turning around.

Now, I can barely keep up with her. She's learned to ride on narrower trails, across and ON country roads. Just the other day, we were in downtown St. Charles and they were setting up for a festival. She rolled right through the middle of everything and then headed off through the grass when she saw a booth she wanted to visit. I just stopped and watched in awe.

The death grip will get better when you get comfortable. Just scan your body every 10 minutes or so, and try to relax those tense muscles.